1. Field of the Invention
This invention relates to a print control apparatus for controlling a page printer such as a laser printer, a light emitting diode (LED) printer and a liquid crystal shutter (LCS) printer, which are referred to as optical printers.
2. Related Art
Recently, optical printers have been extensively used in the field of information processing apparatuses such as a personal computer and a work station. An optical printer is generally connected to the personal computer or work station as a host computer via a print control apparatus.
One example of the conventional print control apparatus is exemplified in Japanese Patent Application Laid-Open Publication (KOKAI) No. 173526/1987, as shown in FIG. 2. In FIG. 2, a train of commands transmitted by a host computer is drawn as a dot pattern into a page buffer 23 by a central processing unit (CPU) 21. When the drawing for one page is completed, data in the first page 231 are read out by a printer adapter unit 24, is processed in a parallel-serial conversion, and then is outputted as a video signal to a printer engine unit 25. The printer engine unit 25 executes the optical printer process to print one page of the paper sheet.
In the above-cited print control apparatus, a plurality of pages 231, 232 and 233 are provided in the page buffer unit 23. Both the drawing and printing processes are carried out simultaneously by performing the printing (reading) to the printer engine unit 25 from the page 232 while performing the drawing (writing) to the page 231, thereby increasing the throughput.
In Japanese Patent Applications 158481/1988 and 164637/1989, the present inventors proposed print control apparatuses, in which both a page buffer memory for a plurality of pages and a printer engine are operated without any idle time and perform command reception, drawing and printing in an overlapped mode so as to carry out the printing operation to be a maximum speed of a printer engine.
With the foregoing conventional apparatuses, a fixed number N of page buffers having a predetermined size s are provided to perform the drawing and the printing. When a page size s1 is larger than the page size s mentioned above, no printing can be performed. To prevent such inconvenience, it is possible to provide the fixed number N of page buffers for the larger size s1. In such a case, the total capacity S of the page buffers will be increased to s1.times.N, which may lead to increase in the cost.
If the page size s1 is much smaller than the page buffer size s, it means that only part of the total page buffer capacity is in use. To be more specific, .DELTA.=(s-s1).times.N of the page buffer area is not used. For example, assume that s stands for A3 size while s1 stands for A4 size. It follows that .DELTA.=A4 size.times.N.